1. Field of the Invention
The present invention relates to an auxiliary contact of an electromagnetic contactor, and more particularly, to an auxiliary contact of an electromagnetic contactor capable of maximizing a time duration for which power is supplied to a magnetic coil for switching a main contact until the main contact is closed.
2. Background of the Invention
Generally, an electromagnetic contactor is a type of electric circuit switching apparatus for performing a mechanical driving and transmitting a current signal using a principle of an electromagnet. The electromagnetic contactor is installed at various types of industrial equipment, machines, vehicles, etc.
The electromagnetic contactor may include a main contact mechanism for performing power supply to a load or disconnecting power supply to the load, and an auxiliary contact mechanism for performing power supply to a magnetic coil of the main contact mechanism or disconnecting power supply to the magnetic coil of the main contact mechanism.
FIG. 1 is a perspective view illustrating a schematic configuration of an electromagnetic contactor in accordance with the conventional art.
The conventional electromagnetic contactor 100 includes a main contact mechanism and an auxiliary contact mechanism 3. The main contact mechanism includes a main contact slide supporting member 1 and a magnetic coil 2. An auxiliary contact pressing portion 1a, which protrudes toward the auxiliary contact mechanism 3, is provided at part of the main contact slide supporting member 1. The auxiliary contact pressing portion 1a drives the auxiliary contact mechanism 3 while being moved up and down together with the main contact slide supporting member 1.
FIG. 2 is a view illustrating a configuration of an auxiliary contact of the electromagnetic contactor of FIG. 1, which shows a closed circuit state. FIG. 3 is a view illustrating a configuration of an auxiliary contact of the electromagnetic contactor of FIG. 1, which shows an open circuit state.
A configuration and an operation of the auxiliary contact mechanism 3 of the conventional electromagnetic contactor will be explained in more detail with reference to FIGS. 2 and 3.
The auxiliary contact mechanism 3 of the conventional electromagnetic contactor includes a contact supporting member 3a, a slide motion supporter 3b, a fixed contactor 3c, a movable contactor 3d, an auxiliary contact spring 3e, and a return spring 3f. 
The contact supporting member 3a is fixedly-installed in a coil assembly accommodation container 4. The fixed contactor 3c is fixedly-installed at the contact supporting member 3a, and a shaft groove 3a1 for inserting the slide motion supporter 3b is formed at the contact supporting member 3a. 
The slide motion supporter 3b moves up and down in a vertical direction through the shaft groove 3a1 of the contact supporting member 3a, and the movable contactor 3d is coupled to a central part of the slide motion supporter 3b. 
The fixed contactor 3c is formed as a pair, and the pair of fixed contactors 3c are installed at the contact supporting member 3a. Each of the fixed contactors 3c includes a terminal portion exposed to outside, and a contact portion disposed therein. One of the fixed contactors 3c may be connected to an external power, and another may be connected to the magnetic coil 2 of the main contact.
The movable contactor 3d moves up and down along the slide motion supporter 3b, and is contactable to or separable from the fixed contactor 3c. 
The auxiliary contact spring 3e is installed between a bottom surface of a central part of the movable contactor 3d, and a spring supporting protrusion formed below the slide motion supporter 3b. The auxiliary contact spring 3e provides an elastic force to press the movable contactor 3d toward the fixed contactor 3c. 
The return spring 3f is installed between a lower end of the slide motion supporter 3b and a bottom surface of the contact supporting member 3a, and provides an elastic force to upward-move the slide motion supporter 3b. 
An operation of the electromagnetic contactor to a closing position (ON′ position) will be explained.
As shown in FIG. 2, once an external control power is applied to the auxiliary contact mechanism 3 in a contacted state between the fixed contactor 3c and the movable contactor 3d, a current flows to the magnetic coil 2 of FIG. 1. If a magnetic force is generated from the magnetic coil 2, a movable core (not shown) and the main contact slide supporting member 1 are sucked downward. Accordingly, a main contact movable contactor (not shown) coupled to the main contact slide supporting member 1 comes in contact with a main contact fixed contactor (not shown) disposed below the main contact movable contactor. As a result, a main circuit is in a closed state.
In this instance, as shown in FIG. 3, the auxiliary contact pressing portion 1a integrally connected to the main contact slide supporting member 1 downward-presses an upper end of the slide motion supporter 3b, while being moved downward. Thus, the slide motion supporter 3b and the movable contactor 3d overcome an elastic force of the auxiliary contact spring 3e and the return spring 3f, and move downward. Accordingly, the movable contactor 3d of the auxiliary contact mechanism 3 is separated from the fixed contactor 3c, and a control power supplied to the main contact through the auxiliary contact mechanism 3 is cut off. Then, the main contact maintains a closed circuit state through a holding current flowing on the magnetic coil 2.
An operation of the electromagnetic contactor to an opening position (‘OFF’ position) will be explained.
Once a control power supplied from outside is completely cut off, a current flowing on the magnetic coil 2 disappears. Thus, a magnetic suction force for downward-sucking the movable core and the main contact slide supporting member 1 disappears, and the main contact slide supporting member 1 is moved upward by an elastic force of the return spring 3f. As a result, the main circuit is in an open state.
As the auxiliary contact pressing portion 1a is also moved upward together with the main contact slide supporting member 10, a pressure which was downward-pressing an upper end of the slide motion supporter 3b disappears. Accordingly, the slide motion supporter 3b and the movable contactor 3d are moved upward by an elastic force of the auxiliary contact spring 3e and the return spring 3f. As a result, the movable contactor 3d of the auxiliary contact mechanism 3 comes in contact with the fixed contactor 3c, and waits for a next control power to be supplied.
However, the conventional electromagnetic contactor has the following problems.
The fixed contactor 3c receives an operating load of the auxiliary contact pressing portion 1a through the slide motion supporter 3b instantly. That is, a movement distance of the slide motion supporter 3b is the same as that of the main contact slide supporting member 1. And a time when the auxiliary contact pressing portion 1a contacts the slide motion supporter 3b determines a time point when the movable contactor 3d is separated from the fixed contactor 3c. 
If such contact time is set at an early time of an operation time of the main contact, the auxiliary contact is open before an operation of the main contact to a closing position is completed. As a result, supply of the control power to the magnetic coil 2 is stopped. This may cause the operation of the main contact to a closing position not to be completed.
Further, if such contact time is set after the operation time of the main contact, a current is continuously supplied to the magnetic coil 2 through the auxiliary contact until an operation of the main contact to a closing position is completed. This may cause damage of the magnetic coil 2 or a chattering phenomenon of the main contact.
In the auxiliary contact of the conventional electromagnetic contactor, since the auxiliary contact spring 3e and the return spring 3f are formed as compression coil springs, time or load taken or required to contact the fixed contactor 3c and the movable contactor 3d each other is almost the same as time or load taken or required to separate the fixed contactor 3c and the movable contactor 3d from each other. That is, a load required when the movable contactor 3d is separated from the fixed contactor 3c is almost the same as a load required when the movable contactor 3d comes in contact with the fixed contactor 3c. This may cause a disadvantage that different operation starting points cannot be set when the main contact is closed and open.